A current trend in portable electronic devices is to focus upon conserving power through lowering the operating voltage of the electronic devices. When the operating voltage of an electronic device is lowered, however, there tends to be an increase in device failures due to the instability of the memory within the electronic device. Many electronic device designs compensate for the lowered operating voltage by incorporating embedded processors having different voltage domains that allow different components to operate at different voltage potentials.
In an effort to provide a means for these embedded processors to communicate with each other, voltage translator circuits interface between these components for translating one voltage potential to another voltage potential. A voltage translator circuit translates one input voltage level to a different output voltage level. This voltage translator circuit usually needs a supply voltage for the input circuitry (VCCA) and a different output supply voltage for output circuitry (VCCB). Specifically, a processor core in a notebook computer may include separate memories, I/O buffer devices, and arithmetic processing logic each having different voltage domains. Each of these separate components may use voltage translator circuits to expedite translation between the voltage digital interfaces. Thereby, each voltage translator circuit is an intermediary circuit formed between a low voltage integrated logic circuit and a high voltage integrated logic circuit located in the various voltage domains.
Generally, a voltage translator circuit provided within a mixed voltage integrated circuit is a mixed voltage integrated circuit having at least two different voltages associated with two different corresponding power supplies. In particular, there may exist a lower voltage that is associated with the core logic and a higher voltage that is associated with the output circuitry. A known voltage translator circuit of this type is shown in FIG. 1.
Two power supplies in the voltage translator design are generally used to manage the difference in supply voltage and input TTL voltage levels on the pin of the device. Without two supplies, there will be an increase in supply current ΔIcc for each input operating at one of the specified TTL voltage levels rather than ground GND or the power supply voltage level VCC. The change in supply current ΔICC represents the supply current change wherein an increase in supply current for each input that is at one of the specified TTL voltage levels rather than 0V or VCC exists.
FIG. 4 shows a performance of a known voltage translator of FIG. 1 wherein the power supply voltage VCC equals 3.6V. The dashed lines represent the supply current. Region A1 illustrates the high to low transition of the input voltage. Prior to the high to low transition, supply current is present in substantial amounts. Region B1 represents when specific voltages transition from low to high. As shown, after the low-to-high transition, large amounts of supply current are present. This type of input cannot satisfy an input TTL voltage level of 1.2V˜3.6V while having a supply voltage of 2.3V˜3.6V without producing a large supply current after the input switches.
In the alternative, a known voltage translator, having only one power supply voltage reference, as shown in FIG. 2 results in having both transistors 26 and 28 on when the voltage at the input In2 is applied. As a result, a large amount of supply current I2 exists causing a large amount of power dissipation. Furthermore, the battery or power supply will be consumed quickly. Thus, in an effort to eliminate the large amount of supply current that exists in a one power supply voltage translator, a voltage translator, having two power supplies, is commonly used that enables the voltage translator to go from one voltage to another without drawing a large amount of supply current. In addition, voltage translator solutions having two supplies are utilized to help manage the difference in supply voltage and input TTL voltage levels on the pin of the device. Without two supplies, there tends to be an increase in supply current ΔICC for each input that is at one of the specified TTL voltage levels rather than ground GND or the maximum power supply voltage level VCC.
Thus, there is a need for a voltage translator having one supply voltage that achieve voltage translation that eliminates supply current or solves the supply current problem.
The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems set forth above.